The invention relates to a device for interrupting the feed of a roving to drawing frames of a spinning machine, whereby each spinning frame comprises a plurality of upper and lower drawing rollers, arranged pairwise, of which the lower drawing roller, located on the feed side of the roving, is provided with a clamping segment, said segment being open in the area opposite the upper drawing roller, said segment being protected against driving in the circumferential direction by a locking device, said device being releasable upon a thread break by means of a broken-end detector which monitors the moving thread.
In a known device of the type described hereinabove (Suessen WST, technical report 1.1-01000D9.79) designated a "slubbing stop," the thread is monitored purely mechanically and the roving feed is likewise interrupted purely mechanically. In this design, an annular clamping segment is mounted on the lower drawing roller, facing the feed side of the roving, said segment being held by a locking device during normal operation, thereby being protected against driving by the drawing roller in the circumferential direction. This locking element comprises a two-armed locking lever, whose second arm is associated with a driving device of a thread feeler, so designed that it executes a greater movement upon a thread break and, by virture of its energy of motion, is then in a position to release the locking lever. The known design offers a simple, sturdy solution for interrupting the roving feed. However, operation requires a certain degree of skill and care, since the thread feeler first must be returned by hand into a preliminary position in which the clamping segment in the locking device can be engaged, whereupon the thread feeler is then shifted to the operating position and brought to bear against the moving thread.
An object of the invention is to design a device of the type described hereinabove in such fashion that it permits simpler operation. This object is achieved in especially preferred embodiments of the invention by virtue of the fact that the locking device, which automatically drops into the locking position, is provided with an electric drive, said drive being controllable by the broken-end detector and energizable for a predetermined time interval, said drive operating in the direction of the unlocking position.
Since the electric drive is energized for only a short time interval, i.e., for only the actual unlocking process, the locking device automatically returns to its locking position. This ensures that it can resume its locking function if only the part to be locked, namely the clamping segment, is returned to the initial position. The broken-end detector can be disregarded as the locking position is resumed, since it has no function during this time.
In an advantageous embodiment of the invention, provision is made for the locking device to be provided with a spring drive which acts in the direction of the locking position. This ensures not only an increase in the certainty that the locking device will automatically return to the locking position, but also excludes the possibility of inadvertent unlocking, caused for example, by machine vibrations or the like.
In an advantageous embodiment of the invention, provision is made for the locking device comprising a locking lever swivelable into a latch in the clamping segment, said lever being tensioned by a spring in the direction of the clamping segment and with which an electromagnet is associated, said magnet being controllable by the broken-end detector and lifting the locking lever out of engagement with the clamping segment when excited. In this manner, a simple, sturdy, and reliable locking device is provided.
It is especially advantageous in this connection if the locking lever, its holder, and the holder for the spring and the electromagnet are designed as a module. This makes it possible to retrofit existing drawing frames with a device of this kind in simple fashion, since only one broken-end detector and the module electrically connected therewith need be provided.
Both mechanically acting and other types of broken-end detectors can be provided according to preferred embodiments of the invention, for example, photosensitive broken-end detectors. The latter have the advantage that there is no need for contact with the thread, so that this type of broken-end detector will not respond if the thread tension should slacken slightly when the machine is shut off.
In another embodiment of the invention, provision is made for the broken-end detector to connect the electromagnet with a previously charge capacitor, which discharges through the electromagnet, when a thread break occurs. This capacitor supplies the energy, required only briefly for unlocking, during its discharge. It is especially advantageous in this connection for the broken-end detector to connect the capacitor with a power supply in the operating position. This ensures that the broken-end detector controls the capacitor being recharged in order to keep the device ready for operation at all times.
In another embodiment of the invention, a provision is made for connecting the capacitor with a counter which receives the discharge current as a counting signal. In this way, the number of thread breaks at the individual spinning units can be determined. However, provision can also be made according to the invention, to install only one counter for one machine, to which counter all the capacitors are connected to deliver counting signals. In this manner, the number of thread breaks per machine is counted.
Other features and advantages of the invention will be apparent from the description of the embodiments shown in the drawings.